Michael Kuchka, Ph.D.
111 Research Drive, B220
Bethlehem, PA 18015
About my research...
lab studies the regulation of expression of organellar genes. We are particularly
interested in the chloroplast of eukaryotic plant cells, and the ways in
which genes located in this organelle are transcribed and the protein products
of these transcripts synthesized. Of special interest is the interaction
between the organellar genetic compartment and the nucleo-cytoplasm. It
is known that nuclear genes of eukaryotic algae and higher plants encode
products which are sent into the chloroplast where they are involved in
the expression of chloroplast genes. Similarly, there is evidence that
the chloroplast sends signals to the nucleus to regulate gene expression
there. We are interested in these interactions and in the communication
between these spatially distinct genetic compartments. We seek to define
the molecular mechanisms by which products of nuclear genes influence gene
expression in the chloroplast and vice versa.
Our experimental organism is the unicellular green alga Chlamydomonas reinhardtii (Chlamydomonas website).
Chlamydomonas cells have a single chloroplast which carries out photosynthesis
in a manner identical to higher plants. The organism is amenable to genetic
analysis - a large collection of mutant strains is available, standard
crosses can be done to define genetic loci, and genes can be cloned by
complementation. We study an important protein, encoded by a chloroplast
gene, which is essential for photosynthesis. This protein, called D2, is
involved in electron transfer reactions through the photosystem II complex.
The synthesis of the D2 protein is blocked by mutations in several different
nuclear genes. Molecular characterization of these mutant strains has determined
that the product of one nuclear gene is necessary for the stabilization
of the mRNA which codes for D2, and the products of two different chloroplast
genes are required for the translation of this mRNA. We are currently in
the process of cloning these nuclear genes to understand how their products
are involved in mRNA stabilization and translation. One gene, AC115, has
recently been cloned. The product of this gene is a small, novel polypeptide
with a hydrophobic stretch of amino acids at its carboxy terminus which
is long enough to be a membrane spanning domain. Our working hypothesis
is that the AC115 gene product is a single- pass trans-thylakoid membrane
protein which functions to stabilize the nascent D2 polypeptide as it is
Ultimately, with a combination of genetic and molecular techniques, our
ambition is to clone additional nuclear genes and define how the products
of these genes are involved in the synthesis of individual gene products
within the chloroplast. This experimentation will help define basic aspects
of the mechanics of RNA stabilization and the regulation of translation.
Godfried Sie, C., Hesler, S., Maas, S., and Kuchka, M. (2012) IGFBP7's susceptibility to proteolysis is altered by A-to-I RNA editing of its transcript. FEBS Letters, 586: 2313 - 2317.
Godfried Sie, C. P. and Kuchka, M. (2011) RNA Editing Adds Flavor to Complexity. Biochemistry (Mosc), 76: 869 - 881.
Rattanachaikunsopon, P., C.
Rosch, and M. R. Kuchka (1999). Cloning and characterization of the nuclear
AC115 gene of Chlamydomonas reinhardtii. Plant Molecular Biology,39: 1-10.
Yohn, C., A. Cohen, C. Rosch,
M. R. Kuchka, and S. P. Mayfield.(1998).Translation of the chloroplast
psbA mRNA requires the nuclear-encoded poly(A)-binding protein, RB47.
Journal of Cell Biology, 142: 435-442.
Wu, H. and M. R. Kuchka (1995).
A nuclear suppressor overcomes defects in the synthesis of the chloroplast
psbD gene product caused by mutations in two distinct nuclear genes of
Chlamydomonas. Current Genetics, 27: 263-269.
Rochaix, J.-D., M. Goldschmidt-Clermont,
Y. Choquet, M. Kuchka, and J. Girard-Bascou (1991). Nuclear and chloroplast
genes involved in the expression of specific chloroplast genes of Chlamydomonas
reinhardtii, in Plant Molecular Biology (ed. R. G. Herman) Plenum Press,
New York, NY.
Kuchka, M. R., M. Goldschmidt-Clermont,
J. vanDillewijn, and J.-D. Rochaix (1989). Mutation at the nuclear NAC2
locus of C. reinhardtii afects the stability of the chloroplast psbD transcript
encoding polypeptide D2 of photosystem II. Cell, 58: 869-876.
Rochaix, J.-D., M. Kuchka,
S. Mayfield, M. Schirmer-Rahire, J. Girard-Bascou, and P. Bennoun (1989).
Nuclear mutations affect the synthesis or stability of the chloroplast
psbC gene product in Chlamydomonas reinhardtii. EMBO Journal, 8:
Day, A., M. Schirmer-Rahire,
M. R. Kuchka, S. P. Mayfield, and J.-D. Rochaix (1988). A transposon with
an unusual arrangement of long terminal repeats in the green alga Chlamydomonas
reinhardtii. EMBO Journal, 7: 1917-1927.
Kuchka, M.R. and Jarvik, J.W. (1987). Short-Flagella Mutants of Chlamydomonas reinhardtii. Genetics 115: 685-691.
Kuchka, M. R., S. P. Mayfield,
and J.-D. Rochaix (1987). Nuclear mutations specifically affect the synthesis and/or
degradation of the chloroplast-encoded D2 polypeptide of photosystem II
in Chlamydomonas reinhardtii. EMBO Journal, 7: 319-324.
Kuchka, M.R. and Jarvik, J.W. (1982). Analysis of Flagellar Size Control Using a Mutant of
Chlamydomonas reinhardtii with a Variable
Number of Flagella. The Journal of Cell Biology, 92: 170-175.